Glutathione-capped gold nanoclusters: photoinduced energy transfer and singlet oxygen generation $$^{\S }$$ §

Abstract

Glutathione-capped gold clusters prepared in an aqueous medium are known to exhibit excellent photosensitizing properties. We have now successfully transferred these gold clusters in an organic medium while retaining all the characteristic excited state properties. These gold clusters can be further modified with organic ligands such as 2-Phenylethanethiol (PET). The gold clusters in organic medium exhibit enhanced emission yield (f = 0.15) compared to that in an aqueous medium (f = 0.08). The excited state lifetimes of 3.7 μs (untreated) and 1.5 μs (PET treated) in toluene are also greater than the lifetime observed in aqueous solution (0.77 μs). By employing laser flash photolysis we are able to induce triplet energy transfer to β-carotene and oxygen. A singlet oxygen generation with the efficiency of 13% was observed in these experiments. The excited state properties of glutathione-capped gold clusters further shows its importance as a photosensitizer in light energy conversion and biomedical applications

Photo/electrocatalysis and photosensitization using metal nanoclusters for green energy and medical applications

“…Talavera et al examined the excited state properties of tetraoctyl ammonium (TOA) capped Au 10–12 (SG) NCs in toluene. 90 The Au NCs exhibited a relatively long-lived triplet excited state, which originated from the ligand to the charge transfer state between the SG shell and the Au core. The quantum yields of 1 O 2 (∼0.13) and the triplet excited state (∼0.15) were evaluated by 1,3-diphenylisobenzofuran (DPBF, a 1 O 2 -selective probe) and triplet–triplet absorption spectra.…”

Fluorescent metal nanoclusters: prospects for photoinduced electron transfer and energy harvesting

“…127 In an another report, they showed triplet energy transfer in 2-phenylethanethiol-treated AuNCs to β-carotene and oxygen with a 13% EnT efficiency using laser flash photolysis in a toluene medium. 128 BSA-protected AuNCs were used as EnT donors and acceptors with DyLight 750 dye and Pacific Blue, respectively. 129…”

The impact of lipid head-groups in GUVs on electron transfer by surface-adsorbed fluorescent gold nanoclusters

“…Reports state that the surface ligands play a commanding role on the donor property of the NCs due to efficient LMCT. 18,28,29 Also, the delocalized electrons donate directly to the metal core due to the influence of the nature of the surface attached ligands. 29 Modulating the process of PET in the presence of suitable electron acceptors (or scavengers), such as MV 2+ , the GSH-AuNCs can become interesting candidates as light energy harvesters.…”

“…[13][14][15][16] Evidences of efficient photosensitization by GSH-AuNCs have been reported in oxygen, hydrogen, and singlet oxygen generation. 17,18 NPs or NCs can preserve their dispersion in biological membranes helping in efficient interactions. 19 Reports are there on such interactions with lipid rafts, 20 bilayers, 21 and vesicles.…”

“…23 Photoinduced electron transfer (PET) is quite common in biocatalysis 24 as well as in singlet oxygen generation. 18 In this context, the GSH-AuNCs are quite useful in visible lightinduced hydrogen formation and light harvesting. 17,25 Hence, we used PET as a tool to investigate the unventured area of the effect of differently charged head groups of lipids (in the form of vesicles) on the extent of PET between the surface adsorbed GSH-AuNCs and externally added MV 2+ ions (electron acceptor).…”